BEIJING (Reuters) - China has ordered the world’s top pork producer, WH Group Ltd, to shut a major slaughterhouse as authorities race to stop the spread of deadly African swine fever (ASF) after a second outbreak in the planet’s biggest hog herd in two weeks.

The discovery of infected pigs in Zhengzhou city, in central Henan province, about 1,000 km (625 miles) from the first case ever reported in China, pushed pig prices lower on Friday and stirred animal health experts’ fears of fresh outbreaks - as well as food safety concerns among the public.

Though often fatal to pigs, with no vaccine available, ASF does not affect humans, according to the United Nations’ Food and Agriculture Organisation (FAO).

ASF has been detected in Russia and Eastern Europe as well as Africa, though never before in East Asia, and is one of the most devastating diseases to affect swine herds. It occurs among commercial herds and wild boars, is transmitted by ticks and direct contact between animals, and can also travel via contaminated food, animal feed, and international travelers.

WH Group said in a statement that Zhengzhou city authorities had ordered a temporary six-week closure of the slaughterhouse after some 30 hogs died of the highly contagious illness on Thursday. The plant is one of 15 controlled by China’s largest pork processor Henan Shuanghui Investment & Development, a subsidiary of WH Group.

Zhengzhou city authorities have banned all movement of pigs and pork products in and out of the affected area for the same six weeks.

Shuanghui said in a separate statement on Friday it culled 1,362 pigs at the slaughterhouse after the infection was discovered.

The infected pigs had traveled 2300 kilometers by road from a live market in Jiamusi city in China’s northeastern province of Heilongjiang, through areas of high pig density to central Henan. Another northeastern province, Liaoning, has culled thousands of pigs since a first case of ASF was reported two weeks ago.

The pigs’ long journey, and the vast distance between the two cases, stoked concerns about the spread of disease across China’s massive pig herd, as well as potentially into Japan, the Korean Peninsula and other parts of Asia.

“When pigs travel long distance, especially under such high temperatures, they would accumulate much waste on the way. And the driver might have to stop many times to rinse the vehicles and the pigs, which will leave the waste all along the way,” said Feng Yonghui, chief researcher at trade website Soozhu.com.

“If there is ASF virus in the waste, it is very easy for pigs transported in other trucks passing by to catch it. It is very risky,” Feng said.

The race in recent years to build vast pig farms in China’s north-eastern cornbelt has also increased the number of pigs being transported across country from farm and market to slaughter and processing in the south.

That underlines the challenge for the government in trying to contain infection.

“The areas of concern now involve multiple Chinese provinces and heighten the likelihood of further cases,” the Swine Health Information Center, a U.S. research body, said in a note.

South Korea doesn’t import pork or pigs from China, but the government has stepped up checks at airports on travelers from the country, and recommended visitors there avoid farms and live markets, the Ministry of Agriculture said on Friday.

In Japan, authorities have ramped up checks on travelers from the affected regions, its Ministry of Agriculture said. It bans imports of raw pork from China.

‘A LITTLE SCARED’

Pig prices dropped on Friday amid concerns about the outbreak on demand for pork, a staple in China’s diet with retail sales topping $840 billion each year. Analysts said farmers may also rush to sell their hogs fearing the infection may spread to their herds.

National hog prices were at 13.97 yuan ($2.03) per kilogram on Friday, down 0.7 percent from Thursday, according to consultancy China-America Commodity Data Analytics.

In central Henan, Hubei and Hunan provinces, prices on average fell more heavily, down 1.4 percent.

“In the short term, there will be a pig-selling spree,” said Alice Xuan, analyst with Shanghai JC Intelligence Co Ltd.

As Zhengzhou city froze pig movements, Heilongjiang authorities were also investigating whether the pigs involved were infected in the northeastern province bordering Russia.

Meanwhile comments on the country’s Twitter-like Weibo highlighted worries about the safety of eating pork, the nation’s favorite meat. The relationship between people and pigs in China is close, with the Chinese word for “home” made up of the character “roof” over the character for “pig”.

Posts expressing concern that infected meat may enter the food stream and fears about whether it is safe to eat pork garnered the most attention.

“A little scared. What will happen if you eat (pork)?” said one poster.

WH Group said on Friday it did not expect the closure of the Zhengzhou slaughterhouse to have any adverse material impact on business, helping its shares rise 0.8 percent after slumping 10 percent on Thursday. Shuanghui shares were up 0.67 percent on Friday afternoon.

The Zhengzhou operation accounts for an “insignificant” portion of WH Group’s operations, the company said, adding it does not expect any disruption to supply of pork and related products as a result of the temporary closure. On Thursday, Shuanghui said it had diverted sales orders to other operations.